Daily weight fluctuation: is mine normal?
Your weight jumps from day to day even though you're doing nothing differently? Paste your weigh-ins or load an export. The checker shows how far your values swing around your trend, which days stand out and how the last two weeks compare with your own history.
Your data never leaves your browser
The calculation runs entirely on your device. No upload, no account and nothing stored on our server.
Order and separators don't matter, comma or dot as decimal mark. Several weigh-ins on the same day are averaged.
Drop a file here or
Apple Health (export.zip or export.xml), Withings (weight.csv or ZIP), Google Fit (Takeout CSV), Happy Scale, Libra, openScale, Trendcurve and any CSV with a date and a weight column.
From yesterday to today
Your fluctuation Example data
This is made-up example data covering twelve weeks, so you can see what a result looks like. Paste your own weigh-ins above.
Assessment
Biggest outliers
| Date | Weigh-in | Trend | Deviation |
|---|
| Date | Weigh-in | Trend | Deviation |
|---|
Share as an image
Create an image of your curve for Instagram, WhatsApp and the like. It is made in your browser.
What can be behind a jump
An overnight jump is almost always water and stomach contents, not fat. These causes are common, and often several act together.
- Salty food: A lot of salt temporarily makes your body hold more water. The scale shows it the next morning, and it goes back down after a few days of normal eating. Read more
- More carbohydrates: Your body stores carbohydrates as glycogen and holds water along with it. After a carb-heavy day the number goes up without any fat being added. Read more
- Exercise: After unusually hard or new training, your muscles hold more water for repair. It shows on the scale for a few days and then settles. Read more
- Menstrual cycle: Many women see higher values in the second half of the cycle and before their period, because hormones shift water balance. They usually drop again once the period starts. Read more
- Digestion: Whatever is still in your gut counts too. Irregular digestion or a large, high-fibre meal the evening before shifts the morning value.
- Time and conditions: In the evening, after eating, with clothes on or on a different floor the scale reads differently than in the morning on an empty stomach. Same conditions make your values more comparable. Read more
Every day, automatically: Trendcurve for iPhone and Android
The app reads your weight from Apple Health or Health Connect and shows your trend and 7-day change, no copying and pasting. Free, no account, your weigh-ins stay on your device.
Automatic in the app, every day
Trendcurve recalculates your trend after every weigh-in, can read your weight from Apple Health and imports your history from Happy Scale, Libra, openScale or Excel. You can ignore single outliers, and markers let you note events such as a salty meal or a new workout. Trend, markers and ignoring weigh-ins are free.
Why does weight fluctuate every day?
The number on the scale is the sum of body fat, muscle, bone, water and whatever is in your stomach and gut right now. Fat changes slowly, while water and stomach contents change from one day to the next. That is why the scale can show more tomorrow even though you did everything right.
How large these swings are differs from person to person. That is exactly why this checker does not compare you with other people but with your own history: how far do your daily values usually sit next to your trend, and does a day fall outside that range?
How to read the result
- Typical fluctuation is the spread of your daily weigh-ins around the trend. A weigh-in that sits this much above or below the trend is ordinary noise for you.
- Days in your usual band shows how many of your weigh-ins were at most one typical fluctuation away from the trend. The remaining days are your outliers.
- The outlier table lists the days with the largest deviation up and down. You can often spot patterns in it, such as a salty meal the day before, exercise or your cycle.
- The assessment compares the last 14 days with the rest of your history: calmer, typical for you or more unsettled.
How the checker calculates
The trend is built as in the Trendcurve app, with exponential smoothing: several weigh-ins on one day are averaged, and each new weigh-in pulls the trend 10 percent towards it. Typical fluctuation is the standard deviation of daily weigh-ins from the trend over the last 90 days. The first 7 days with weigh-ins are left out while the trend settles, as long as enough values remain afterwards.
For the assessment, the checker divides the spread of the last 14 days by the spread of the whole period. Below 0.8 times, the phase counts as calm, above 1.25 times as unsettled, and in between as typical for you. These limits are a setting of the checker, not a medical norm. The comparison appears from 28 analysed days with weigh-ins, at least 5 of them in the last 14 days.